Cloudformation: How to pass a string through cloudformation script into UserData?

Question

Cloudformation command:

- aws cloudformation create-stack --stack-name stackName --template-body file://cloudformation.yaml --parameters ParameterKey=keyName,ParameterValue=myKeys

I need to paste env variable into UserData cloudformation sctipt. So at the end it would have docker pull quay.io/apple/myRepo:myVarName

UserData:
      Fn::Base64: !Sub |
        docker pull quay.io/apple/myRepo:master

!Join [ ":", ["quay.io/apple/myRepo", !Ref myParameterName ] ] — jordanm
– jordanm, Commented Jun 29, 2020 at 20:32
I see. But how to you actually pass it i? Can you share example? — Sergio13
– Sergio13, Commented Jun 29, 2020 at 20:42
Your post already includes an example of passing parameter values through the CLI — jordanm
– jordanm, Commented Jun 29, 2020 at 20:58
Those names used in cf file too ofter and it sort of confusion. I would appreciate simple example — Sergio13
– Sergio13, Commented Jun 29, 2020 at 20:59

Marcin · Accepted Answer · 2020-06-29 22:56:03Z

1

If you executed aws cloudformation create-stack with the following parameters:

--parameters ParameterKey=keyName,ParameterValue=myKeys

in your template you need to have Parameters section:

Parameters:

  keyName:
    Type: String

Then in your UserData you would reference parameter keyName as follows:

UserData:
  Fn::Base64: !Sub |
     param_value=${keyName}

answered Jun 29, 2020 at 22:56

Marcin

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7 Comments

Sergio13 Over a year ago

Would it look like this if you would have to concatenate it? docker pull quay.io/repo/apple:${branchName}

Marcin Over a year ago

@Sergio13 What do you mean that it does not work? Any error messages? What do your updated UserData and Parameters sections look like now?

Sergio13 Over a year ago

No error messages, it stops execution at that line, and if I navigate to ec2 instance I have no access to that branchName var.

Sergio13 Over a year ago

My code: Parameters: keyName: Description: Name of an existing EC2 KeyPair to enable SSH access to the EC2 Instances Type: "AWS::EC2::KeyPair::KeyName" branchName: Type: String Resources: launchTemplate: Properties: LaunchTemplateData: UserData: Fn::Base64: !Sub | #!/bin/bash -xe docker pull quay.io/****/****:${branchName}

Sergio13 Over a year ago

You answer actually worked. The issue was with codefresh way to pass data into cf script. It just needed to be assigned into var before passing it

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